October 07, 2018

The Washington Naval Treaty

When World War I ended, the world looked poised on the verge of another naval arms race. The United States, which had aimed at parity with Britain under the 1916 Naval Program, was talking about an even larger fleet program, to firmly surpass the Royal Navy. In the Pacific, Japan was building the so-called 8-8 fleet, aiming to have 8 new battleships and 8 new battlecruisers. This would pose a major threat to British and American holdings in the Far East. Britain would traditionally have simply outbuilt these threats as they had with Germany a decade earlier, but the war had left them nearly bankrupt. So when American Secretary of State Charles Evans Hughes called a conference on naval armaments in November 1921, all three countries showed up, as did France and Italy.1

Hughes opened the conference with a dramatic series of proposals, calling for the immediate suspension of all capital ships currently under construction, no new construction for the next 10 years and rules on when older ships could be replaced. Older ships would be scrapped to bring capital ship tonnages in Britain, the US and Japan to 600,000, 500,000 and 300,000 respectively.2 All other categories of ship would be limited on similar lines.

Memorial Continental Hall, where the Conference was held

The Americans obviously accepted these proposals, and the British were mostly in agreement, too. The Japanese, however, wanted major modifications. They had calculated that they needed 70% of the strength of either of the other powers to be able to win in the Western Pacific. Disputes over the tonnage ratio held up the conference for several months, but they eventually managed to trade acceptance of the American tonnage ratio for a clause banning the construction of new bases or fortifications in most of the Western Pacific.

Mutsu early in her career

The Japanese also raised issues with the proposed list of ships to be scrapped. Under Hughes' original proposal, each power would retain a single "post-Jutland" battleship. The British had Hood, the Americans Maryland, and the Japanese Nagato. But the Japanese delegation pointed out that Nagato's sister ship, Mutsu, had commissioned a few weeks before. In addition, she had been largely funded by donations from schoolchildren, and the blow to public morale from scrapping the completed ship would have been too much.

Colorado, one of the American ships spared under the treaty

Eventually, all three delegations reached a compromise. In exchange for more scrappings among the older ships, the Japanese would get to keep Mutsu while the Americans completed Colorado and West Virginia, both sisters to Maryland and over 90% complete. The British, who had no battleships under construction, were to be allowed to build two new battleships subject to the treaty restrictions. This meant that the qualitative disadvantage of the British would be wiped out, and the final tonnage allowances were 525,000 for the US and UK, 315,000 for Japan and 175,000 for France and Italy.3

HMS Nelson, lead ship of the class the British built under the treaty.

The drafters of the treaty didn't expect warships to last forever, and after the 10-year holiday expired, warships could be replaced when they reached 20 years of age. Any replacement battleships would have to be 35,000 tons or less, and couldn't mount guns larger than 16". There was also a provision allowing reconstruction of existing ships, but only to improve their resistance against air or submarine attack. 3,000 tons could be added to any existing ships in the form of bulges or improved deck armor.4 Any changes to side armor or the caliber, number, or mounting of main guns were prohibited.5

HMS Raleigh, of the Hawkins class

Another point of contention was the restriction on smaller ships, and there the original Hughes proposal failed. The British came in with an attempt to ban submarines, as memories of the U-boat offensive were still fresh. The French in particular opposed them, and the conference ended with no restrictions on submarines. The other British effort was more successful. They were unwilling to accept the proposed limits on cruisers, as they as they believed they needed 70 to police their far-flung Empire, far more than the US or Japan wanted. Eventually, the dispute grew so heated that any limitation on number of ships or aggregate tonnage for non-capital ships was scrapped, those being defined as ships of less than 10,000 tons and mounting weapons of 8" caliber or smaller. This limit was based on the British Hawkins class, and was soon adopted as the standard for the "treaty cruisers".

Saratoga transiting the Panama Canal in the late 1920s

But it was obvious even at the time that aircraft carriers were not going to remain within these limits, and would have to be dealt with separately. The US and Britain each got 135,000 tons of carriers, while Japan received 81,000. Individual carriers were limited to 27,000 tons, and to prevent someone building a battleship with a flight deck and calling it a carrier, aircraft carriers were limited to no more than 10 8" guns. A clause was included allowing conversion of capital ships currently under construction to carriers, with a higher limit of 33,000 tons. The US converted Lexington and Saratoga,6 while the Japanese did the same with Akagi and Kaga.

Pensacola, the first American treaty cruiser

But simply defining limits in tons was not enough. Tonnage is a complicated measurement, and some consistent standard would have to be agreed upon. The most obvious metric would be to measure with some fraction of fuel, water, ammunition, and provisions, one of full, two-thirds, or half. But the United States objected to this. The American delegates pointed out that, thanks to its Pacific obligations, their warships would need substantially longer range than those of other nations. Thus, an American warship of a given treaty tonnage under such a metric would be substantially weaker than one of, say, Italy, which would be built only for short-range deployments in the Mediterranean.

Italian treaty cruiser Bolzano

The resulting compromise was the creation of Standard or Treaty displacement, defined as displacement “complete, fully manned, engined, and equipped ready for sea, including all armament and ammunition, equipment, outfit, provisions and fresh water for crew, miscellaneous stores, and implements of every description that are intended to be carried in war, but without fuel or reserve boiler feed water on board.” Obviously, no ship ever was in this condition, but it proved a useful compromise.7 The American ship would still be weaker than its Italian counterpart, all else equal, but it would be a much more even fight.

Mikuma of the Mogami class, probably the most egregious violators of the treaty tonnage limit

Finally, in February 1922, all powers were in agreement and the treaty was signed. Despite extensive cheating by the Japanese, which I will discuss at some point, the treaty proved successful in stopping the brewing arms race and cutting expenditure on warships. Despite complaints from all powers involved, in retrospect it was clearly a good thing for everyone. The Japanese were granted much more tonnage than their relative economic status would have allowed them in an all-out building race,8 as was graphically demonstrated during the 1940s. The US and Britain managed to gain political cover for their navies in the immediate post-war years, when economy was much on the minds of governments, and avoided destroying their relationship over the question of ruling the waves.9 The Washington Treaty was later superseded by the 1930 and 1936 London Naval Treaties, but they were essentially extensions of the foundations laid in the US, foundations which shaped the battleship to the end of its life.

1 This was all of the world's major naval powers. Germany was disarmed by the Treaty of Versailles, while Russia was in complete chaos and nobody else had enough ships to be worth inviting to the table.

2 In theory, the ratio was supposed to be 5:5:3, but Britain had suspended building earlier, so Hughes planned to give them extra tonnage to compensate.

3 France and Italy had a bunch of weird exceptions under the treaty. The biggest one was that they were allowed to build a few capital ships during the holiday, although neither of them took advantage of this. I'm mostly ignoring them because the US-UK-Japan aspects had a much larger impact on naval affairs.

4 This armor would have also helped in a long-range gun duel, although the delegates seem not to have realized that.

5 This provision became controversial during the interwar years. As improved fire control pushed gun ranges up, there was a need to increase maximum gun elevation on older ships to keep up. The US initially interpreted this provision to ban such reconstructions, but the British did not, and the US later followed suit.

6 It proved impossible to make effective carriers out of the Lexingtons on 33,000 tons, so the US took the position that the 3,000-ton allowance for improved protection against air and submarine attack also applied to the converted carriers. For pretty much their entire careers, these ships were carried on the books as 33,000 tons with an asterisk, instead of the true 36,000 ton displacement.

7 Standard displacement should not be confused with other types of displacement, which attempt to reflect actual states of the ship, but it often is. See my article on measurements for more details.

8 Japan's GDP was only 18% of America's, and they got 60% as much tonnage.

9 On the other hand, the 10-year holiday, later extended another five by the 1930 London Treaty, did terrible damage to Britain's privately-owned battleship construction industry. David Beatty, one of Britain's delegates, had called for continued construction at a reduced pace in place of the holiday, but he had lost.


  1. October 07, 2018Dusk_Star said...

    What was the US rationale for giving the British an equivalent tonnage if their economy was in such a dire state? Solidarity against the Japanese or something of that sort?

  2. October 07, 2018bean said...

    It's the other way around. The British giving the Americans parity was seen as huge. A year or two earlier, there was talk of war if the US tried for parity, and it was at least a bit serious. Then the depth of the economic problems became apparent, and both sides compromised.

  3. October 07, 2018Cassander said...

    You criminally understate Hughes' brilliance in pulling this off. In 1916, the US officially dedicates itself officially to building a navy second to none. By 1920, they are very behind on this score, with the brits having a couple dozen more dreadnoughts than they do. The US has the industrial capacity to catch up if it chooses, but congress wasn't going to be enthusiastic about it, and might very well have refused to pay for a naval race.

    Hughes knows this, and by virtue of a brilliant opening, manages to establish the entire conference on the basis of american terms. He gets the british empire, ruler of the waves for at least two centuries, to willingly scrap their margin of superiority over the US fleet, at a stroke giving the US a naval parity congress almost certainly wouldn't have paid for, while throwing a wrench in their alliance with Japan. It's one of the greatest diplomatic feats in American history, an achievement almost on a level (in terms of difficulty) with Franklin's mission to france in the 1770s.

  4. October 07, 2018Cassander said...

    It occurs to me that we should put together a list of most entertaining treaty dodges. The lexington's 3000tons is probably the best, but there are other strong contenders, the Mogami's being designed with 6" guns but turret rings exactly the same size as their 8" mounts, the US reclassifying half of the ammunition storage in one of its cruiser classes as "emergency reserves", using "reserve feed water" to balance turrets instead of lead. You can probably think of some good ones.

  5. October 08, 2018bean said...

    I think that you overstate the magnitude of the US victory. The 1916 "second to none" program was authorized in an entirely different diplomatic environment from that of 1920. In 1916, there was serious thought that we might have to fight Britain. In 1920, we had just left the war as allies. And Washington had the same effect on the British fleet as most arms-control treaties have had on the Russian nuclear arsenal. There's some trimming, but it's mostly getting diplomatic credit for something you were going to do anyway. Dreadnought had already gone into reserve before the end of the war, and they simply didn't have the manpower or cash to keep all of their ships in commission.

    The one decent dodge you don't mention is keeping the TDS dry most of the time so you dont' have to count it. I'm not sure about the feedwater balance. Who did that?

  6. October 08, 2018ADifferentAnonymous said...

    What was supposed to happen if a war broke out between treaty powers, or for that matter between a treaty and a non-treaty power (if one emerged)? Would destroyed ships be replaceable? If so, would you have to wait for a ship to be sunk before laying down the replacement?

  7. October 08, 2018bean said...

    If war broke out between the treaty powers, then in practice the treaty was null and void. Basically all of the treaty battleships completed overweight, as they were commissioned after the treaties (London, but the principle is the same) had lapsed at the start of WWII. There was a provision in the treaty (full text)to cover vessels that were lost or sunk:

    Part 3, Section I (c) In case of loss or accidental destruction of capital ships or aircraft carriers, they may immediately be replaced by new construction subject to the tonnage limits prescribed in Articles IV and VII and in conformity with the other provisions of the present Treaty, the regular replacement program being deemed to be advanced to that extent.

  8. October 08, 2018ADifferentAnonymous said...

    You say null and void "in practice"--is that to say it could still apply in theory? I wonder about a Franco-Italian scrap, which unlike WWII would have neutral parties stronger than the belligerents as potential enforcers.

  9. October 08, 2018bean said...

    That's a good question, but not one I have the answer to. Technically speaking, there was never a war between the treaty powers. Germany was never a signatory, although they'd agreed to abide by the terms of the London Treaty under the Anglo-German Naval Agreement. Italy and Japan both withdrew from Second London in 1936, well before either entered the war.

    That said, I'm not sure there's a good answer. Particularly before WWII, there wasn't an International Legislature or an International Supreme Court, so international law was far more fluid than normal domestic law. There are a couple clauses in the treaty which restrict what powers can do in time of war (not taking over ships they were building for export, for instance), which suggests that the treaty would stay in force during a war. But I think it rather depends on the war.

    If France and Italy go to war in 1925, then I don't think that would totally collapse the treaty structure. Battleships take a long time to build, so it's not like they're just going to suddenly order a fleet of 50,000-ton dreadnoughts. In fact, there was not a single case of a proper battleship laid down after a power entered a war that participated in that war. Vanguard came close, but didn't quite make it. I'm sure that the finer points of the tonnage rules would go out the window very quickly (suddenly all the space for war reserve ammo gets filled and extra AA guns show up) but the big concern of the other powers is the belligerents getting a long-term advantage, and that's just not going to happen. In all likelihood, the extra stuff comes off at the end of the war, and everything goes back to normal. It might have been a bigger problem under the London treaties which placed total tonnage limits on smaller ships.

  10. October 08, 2018cassander said...


    I think that you overstate the magnitude of the US victory. The 1916 “second to none” program was authorized in an entirely different diplomatic environment from that of 1920. In 1916, there was serious thought that we might have to fight Britain. In 1920, we had just left the war as allies.

    Which is precisely why congress was unlikely to follow through in 1920

    And Washington had the same effect on the British fleet as most arms-control treaties have had on the Russian nuclear arsenal. There’s some trimming, but it’s mostly getting diplomatic credit for something you were going to do anyway.

    I disagree. Some of those ships were going to get scrapped, but by no means all of them. And the Washington treaty was (A) one of the first that resulted in weapons getting scrapped and (B) had a much more disproportionate scrapping rate than the nuke treaties.

    Dreadnought had already gone into reserve before the end of the war, and they simply didn’t have the manpower or cash to keep all of their ships in commission.

    The win wasn't killing dreadnought, it was getting the brits to accept naval parity in principle,

  11. October 08, 2018bean said...

    I get that parity was a big win. But I think the British acceptance had a lot more to do with economics and a lot less to do with brilliant American diplomacy. Note that the original proposal for battleship tonnage was adopted more or less unchanged. If anything, the British actually gave up a tonnage advantage because they knew they were getting better ships.

  12. October 09, 2018ADifferentAnonymous said...

    Was the spirit of the treaty at least kind of binding? Those dodges don't sound like the most egregious things you could do within the letter of the treaty, unless the fine print was really really good.

    I'm guessing that if you did anything too obvious--like, say, multiple fifteen-year-old ships 'accidentally' sinking in harbor with no casualties--there would have been diplomatic repercussions?

  13. October 09, 2018bean said...

    Pretty much. There was significant debate about how rigorously a lot of clauses had to be applied, and the Japanese disregarded the tonnage clauses when they felt like it, but it did constrain numbers, and size to a reasonable extent. (It's easy to report false draft numbers and hide maybe 30% overweight. More than that, and it's increasingly obvious you're cheating.)

    And yeah, if someone started to play weird games, it would get noticed.

  14. October 10, 2018Alex said...

    Apparently cryptography also played a role here - the Japanese apparently went into the treaty negotiations asking for an 80% ratio, but the Americans had read their orders and knew they'd expected to be bargained down to 70%, and were willing to go as low as 60% in extremis for the purpose of saving the treaty.

    Unfortunately, this seems to have had the effect of sapping Japanese support for the treaty and contact with the West generally, which may have contributed to them going crazy in the following decades.

  15. October 10, 2018bean said...

    True. I should probably point out that I was not really trying to write a diplomatic history of the treaty, instead giving something that looked at what the results were and how they impacted battleship design going forward. I'm sure I'll revisit the subject at some point, but that's a rather different genre than what I was going for here.

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